JP H7-217417 A discloses an engine system in which a cam for driving an intake valve is switched between two types of cams. One is an intake cam for low engine speed and the other is an intake cam for fast engine speed. During engine stop, the conventional system keeps driving the engine for a predetermined period to switch the intake cam for high engine speed to the intake cam for low engine speed. If the engine system performs the cam switch after the engine restarts, an engine start failure may occur in association with a delay caused by the cam switch. In this regard, the conventional system performs the cam switch before the engine restarts, a good engine restart can be achieved.
JP H7-217417 A does not discuss details of the predetermined period. In general, it is expected that the predetermined period is set to be a reasonable period enough to complete the cam switch for sure. However, such period prolongs the driving period of the engine and causes reduction of fuel consumption. And it is obvious that such problem is especially prominent when the number of cylinders of the engine increases. As just described, there is room for improvement on the conventional system with regard to the fuel consumption of a multi-cylinder engine.
The present disclosure addresses the above problem, and an object of the present disclosure is, in a multi-cylinder engine system driving an intake valve with two types of cams, to suppress reduction of fuel consumption in association with the cam switch during the engine stop which is performed in anticipation of the engine restart.